I assume this is just the $29 charger attached to a base, but how much does the base weigh? Will it slide easily? Is there some sort of additional functionality that warrants an almost 300% higher price?

According to Apple's own testing conducted in August 2016 using pre-production Apple Watch Series 1, Apple Watch Series 2 and Apple Watch Edition, each paired with an iPhone, a 100% charge was achieved in 2 hours.

The charging dock is essentially the exact same as the magnetic charger that comes standard with an apple watch.

Would like to leave on a nice looking stand without constantly charging since don't wear my Apple Watch every day and have a great looking stand by Just Mobile. However, if placed on the stand which houses the watch charger it will automatically switch it on if I have it turned off, why?

Any band that does not split in the middle will not work lying down on the charger. So any band, such as the Milanese, loop, Link bracelet, and some of the Hermes' collection will have to be charged on it's side.